JP6778379B2 - Impact Resistant Reactive Hot Melt Adhesive Composition - Google Patents

Description

The present invention relates to a reactive hot melt adhesive composition, and more particularly to a reactive hot melt adhesive composition having excellent impact resistance.

Hot-melt adhesives are solvent-free adhesives that have less impact on the environment and the human body, and can be adhered in a short time, making them suitable for improving productivity. In the industrial world such as bookbinding, textiles, and building materials. Widely used.
Hot-melt adhesives can be broadly divided into two main components: thermoplastic resins and reactive resins. EVA (ethylene vinyl acetate copolymer) is mainly used as the hot melt adhesive whose main component is a thermoplastic resin, and it is a so-called hot melt adhesive.
On the other hand, the hot melt adhesive containing the main component as a reactive resin mainly uses a urethane prepolymer at the end of the isocyanate group, and is called a reactive hot melt adhesive. After bonding, the reactive hot melt adhesive develops a certain level of adhesive strength in a short time by cooling and solidifying the adhesive itself. After that, the terminal isocyanate group of the urethane prepolymer reacts with the moisture in the air or on the surface of the adherend to increase the molecular weight and crosslink the urethane prepolymer to form an adhesive layer and develop heat resistance during heating. However, it shows good adhesive strength (adhesive strength).

Conventionally, double-sided tape has often been used to bond parts such as display parts of wearable terminals such as mobile phones. Since the wearable terminal is carried around, it may be accidentally dropped when it is carried or used. Therefore, the adhesive portion of the wearable terminal is required to have impact resistance so that the parts bonded together due to the impact at the time of dropping do not fall off (for example, Patent Document 1).
Further, in recent years, with the miniaturization of wearable terminals, the area of the adhesive portion between parts tends to become smaller, and the number of parts having complicated shapes increases, so that sufficient adhesive strength cannot be obtained by the conventional adhesive method using double-sided tape. I had a problem. It is said that tape processing becomes difficult when the adhesive width of the tape is 0.7 mm or less.

Patent Documents 2 and 3 are disclosed as adhesives in consideration of drop impact resistance. Here, the hot melt adhesive disclosed in Patent Document 2 is an adhesive containing an organic solvent, and there is a concern from the viewpoint of environmental impact. Further, the epoxy adhesive disclosed in Patent Document 3 is a two-component mixed type adhesive, and has a problem in handling.

Japanese Unexamined Patent Publication No. 2012-67315 Japanese Unexamined Patent Publication No. 2014-177574 Japanese Patent Application Laid-Open No. 2014-512436

The present invention provides a reactive hot-melt adhesive composition that is solvent-free, one-component, and has impact resistance, while having coating properties that allow parts to adhere to each other in extremely small areas. To provide.

In order to solve the above problems, the present invention comprises (1) a urethane prepolymer (i) having an isocyanate group obtained by reacting a polyester polyol (A), a polyether polyol (B) and an isocyanate (C), and a urethane. A reactive hot-melt adhesive composition containing a prepolymer (i) and a non-reactive component (ii), wherein the mechanical properties of the obtained adhesive layer are tensile elasticity defined by JIS K-7127. Provided is a reactive hot melt adhesive composition having a ratio of 40 MPa or less, a tensile fracture stress of 15 MPa or more, and a breaking point elongation of 1,000% or more.
(2) The reactive hot melt adhesive composition according to (1), wherein the polyester polyol (A) is composed of a crystalline polyester polyol (A-1) and an amorphous polyester polyol (A-2). is there.
(3) The non-changing polyester polyol (A-2) is composed of a polyester polyol (A-2-1) having a molecular weight of 3,000 or less and a polyester polyol (A-2-2) having a molecular weight of 5,000 or more (1). Alternatively, the reactive hot melt adhesive composition according to (2) is provided.
(4) The component (ii) that does not react with the urethane prepolymer (i) is polybutene, polybutadiene, ester plasticizer, acrylic plasticizer, rosin resin (rosin resin, rosin ester resin, hydrogenated rosin ester resin), The reactive hot melt adhesive composition according to any one of (1) to (3), which is one or more selected from terpene-based (terpene resin, hydrogenated terpene resin), is provided.
(5) Any of (1) to (4) in which the amount of the component (ii) that does not react with the urethane prepolymer (i) is 0.1 to 10 parts by mass with respect to 100 parts by mass of the urethane prepolymer (i). It provides the reactive hot melt adhesive composition according to the above.

According to the present invention, a reactive hot-melt adhesive composition which is a solvent-free type, a one-component type, and also has impact resistance while having a coatability capable of adhering parts to each other in a very small portion can be obtained. To provide.

The reactive hot-melt adhesive composition of the present invention (hereinafter, may be abbreviated as an adhesive composition) is obtained by reacting a polyester polyol (A), a polyether polyol (B) and an isocyanate (C). A reactive hot-melt adhesive composition containing a urethane prepolymer (i) having an isocyanate group and a non-reactive component (ii), and the mechanical properties of the adhesive layer obtained from this adhesive composition. However, it is characterized in that the tensile reactivity defined by JIS K-7127 is 40 MPa or less, the tensile fracture stress is 15 MPa or more, and the break point elongation is 1,000% or more.
The mechanical properties of the adhesive layer obtained from the reactive hot-melt adhesive composition of the present invention are characterized by being an adhesive layer having a tensile elastic modulus of 40 MPa or less as defined by JIS K-7127. is there. The tensile elastic modulus is preferably in the range of 2 to 40 MPa, and particularly preferably in the range of 5 to 30 MPa. Since the adhesive layer has a tensile elastic modulus of 40 MPa or less, it becomes a flexible adhesive layer and can be expected to have impact resistance.

Next, the mechanical properties of the adhesive layer obtained from the reactive hot-melt adhesive composition of the present invention are that the tensile fracture stress defined by JIS K-7127 is 15 MPa or more. The upper limit is 100 MPa, and the preferable tensile fracture stress is in the range of 15 to 50 MPa, particularly preferably in the range of 15 to 40 MPa. Since the adhesive layer has a tensile fracture stress of 15 MPa or more, it becomes a tough adhesive layer, and improvement in adhesive strength can be expected.

Further, the mechanical properties of the adhesive layer obtained from the reactive hot melt adhesive composition of the present invention are that the elongation at break point defined by JIS K-7127 is 1,000% or more. The break point elongation is preferably in the range of 1,000 to 3,000%, particularly preferably in the range of 1,200 to 2,000%. Since the adhesive layer has a breaking point elongation of 1,000% (10 times) or more, it becomes a flexible adhesive layer, and improvement in impact resistance can be expected.

The polyester polyol (A) used in the present invention is, for example, a polyhydric alcohol having 2 to 15 carbon atoms and 2 or 3 OH groups, one or more polycarboxylic acids, and 2 to 14 carbon atoms. It is produced by a polycondensation reaction with a polycarboxylic acid having (containing a carbon atom in a carboxyl group) and having 2 to 6 carboxyl groups. In the present invention, a dicarboxylic acid is preferred, which produces a linear polyester diol with the diol or a branched polyester triol with the triol. Conversely, the branched polyester triol can also be obtained by reacting the diol with a tricarboxylic acid. As the alcohol component of the polyester polyol, for example, the following compounds can be used: ethylene glycol, 1,2-propanediol, 1,3-propanediol, isomeric butanediol, pentanediol, hexanediol, 2, 2-Diol-1,3-propanediol, 2-methylpropanediol, 1,6-hexanediol, 2,4,4-trimethylhexanediol, 2,2,4-trimethylhexanediol, cyclohexanediol, 1,4 -Cyclohexanedimethanol, or aromatic diols such as 4,4'-dihydroxydiphenylpropane, bisphenol A, bisphenol F, pyrocatechol, resorcinol, hydroquinone. Suitable carboxylic acids are, for example, the following compounds: phthalic acid, isophthalic acid, terephthalic acid, maleic acid, dodecylmaleic acid, octadecenylmaleic acid, fumaric acid, adipic acid, 1,2,4-benzenetricarboxylic acid. , 1,2,3-Propanetricarboxylic acid, maleic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, sebacic acid, cyclohexane-1,2-dicarboxylic acid, 1,4-cyclohexanediene-1,2-dicarboxylic acid acid. In addition, instead of the carboxylic acid of these compounds, the anhydride can also be used.

The polyester polyol (A) is composed of a crystalline polyester polyol (A-1) and an amorphous polyester polyol (A-2), and the distinction between crystalline and amorphous is judged at 25 ° C. That is, in the polyester polyol (A) of the present invention, a polyester polyol in a crystalline state at 25 ° C. is a crystalline polyester polyol (A-1), and a polyester polyol in a non-crystalline state at 25 ° C. is an amorphous polyester polyol (a non-crystalline polyester polyol). A-2).

In addition, the number average molecular weight of the crystalline polyester polyol (A-1) is preferably in the range of 500 to 10,000, preferably in the range of 1,000 to 8,000, from the viewpoint of waterproofness and adhesiveness. Is. The number average molecular weight of the crystalline polyester polyol (A-1) is a value determined by polystyrene conversion by gel permeation chromatography (GPC). For GPC measurement, Hitachi Chemical's HPLC packing columns "Gelpack GLA130-S", "Gelpack GLA150-S" and "Gelpack GLA160-S" are connected and used at a flow rate of 1.0 ml / min using tetrahydrofuran as an eluent. Then, the column temperature is 40 ° C., and the detector is measured using RI.

The amorphous polyester polyol (A-2) is composed of a polyester polyol (A-2-1) having a molecular weight of 3,000 or less and a polyester polyol (A-2-2) having a molecular weight of 5,000 or more.
The number average molecular weight of the amorphous polyester polyol (A-2-1) having a small molecular weight is 3,000 or less. The lower limit is 500, which is determined from the viewpoint of improving the initial adhesiveness. The number average molecular weight of the amorphous polyester polyol (A-2-1) having a small molecular weight is preferably in the range of 500 to 3,000, and particularly preferably in the range of 1,000 to 3,000.

Further, the amorphous polyester polyol (A-2) having a large molecular weight has a number average molecular weight of 5,000 or more. The upper limit is 20,000, which was determined from the viewpoint of improving waterproofness, flexibility, impact resistance, coatability, and the like. The number average molecular weight of the amorphous polyester polyol (A-2-2) having a large molecular weight is preferably in the range of 5,000 to 12,000, and particularly preferably in the range of 5,000 to 10,000. The number average molecular weight of the amorphous polyester polyol (A-2-1) and the amorphous polyester polyol (A-2-2) is the same as the number average molecular weight of the crystalline polyester polyol (A-1). Similarly, it is a value obtained by GPC (gel permeation chromatography) measurement.

The polyether polyol (B) imparts excellent workability, adhesiveness, waterproofness, flexibility, etc. by adjusting an appropriate melt viscosity and open time (bonding time) after coating, for example. , Polyethylene glycol, polypropylene glycol, polybutylene glycol, polytetramethylene glycol, ethylene oxide-modified polypropylene glycol and the like can be used.
The number average molecular weight of the polyether polyol (B) is preferably in the range of 500 to 6,000, more preferably in the range of 1,000 to 5,000, from the viewpoint of adhesiveness and flexibility. The number average molecular weight of the polyether polyol (B) is a value obtained by measuring by the same method (GPC) as the number average molecular weight of the crystalline polyester polyol (A-1) described above.

As the isocyanate compound (C) of the present invention, it is preferable to use diisocyanate, for example, diphenylmethane diisocyanate, dimethyldiphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, p-phenylenediisocyanate, isophorone. Diisocyanate or the like can be used.

Therefore, in the reactive hot melt adhesive composition of the present invention, the polyisocyanate compound and the polyol may be mixed to form a urethane prepolymer (i), or the polyisocyanate compound and the polyol may be mixed with a urethane prepolymer (i) in advance. ) May be synthesized and added to the adhesive composition of the present invention.
When synthesizing the urethane prepolymer (i) having an isocyanate group, the mixing ratio of the polyisocyanate compound and the polyol in the present invention is such that the isocyanate group (NCO) equivalent of the polyisocyanate compound / the hydroxyl group (OH) equivalent of the polyol is 1. It is .6 to 3.0, preferably in the range of 1.8 to 2.5. If the NCO / OH ratio is less than 1.6, the viscosity of the obtained prepolymer (i) becomes high and the coating workability is deteriorated. On the other hand, if the NCO / OH ratio exceeds 3.0, foaming is likely to occur during the moisture curing reaction, which may reduce the adhesiveness.

The component (ii) that does not react with the urethane prepolymer (i) of the present invention is polybutene, polybutadiene, ester plasticizer, acrylic plasticizer, rosin resin (rosin resin, rosin ester resin, hydrogenated rosin ester resin). , One or more selected from terpen type (terpene resin, hydrogenated terpene resin).
The urethane prepolymer (i) and the non-reactive component (ii) do not have active hydrogen such as a hydroxyl group and are required not to react with the urethane prepolymer (i). From the viewpoint of adhesiveness and the like, the range of 0.1 to 10 parts by mass of the reactive hot melt adhesive is preferable, and the range of 0.2 to 5 parts by mass is more preferable.
Since the urethane prepolymer (i) and the non-reactive component (ii) are not incorporated into the urethane prepolymer which is the main component, the effect of alleviating the impact when the adhesive layer obtained from the adhesive is applied is obtained. Be done.

In a reactive hot melt adhesive composition in which the amount of the component (ii) that does not react with the urethane prepolymer (i) of the present invention is 0.1 to 10 parts by mass with respect to 100 parts by mass of the urethane prepolymer (i). is there. A reactive hot-melt adhesive composition having excellent impact resistance can be obtained when the amount of the non-reactive component (ii) is 0.1 part by mass or more with respect to 100 parts by mass of the urethane prepolymer (i). On the other hand, if the amount of the non-reactive component (ii) is 10 parts by mass or less with respect to 100 parts by mass of the urethane prepolymer (i), good adhesive strength is exhibited.

Further, the reactive hot melt adhesive composition includes a catalyst (dibutyltin dilaurate, dibutylthione octate, dimethylcyclohexylamine, dimethylbenzylamine, trioctylamine, etc.), a pigment, an antioxidant, an ultraviolet absorber, and a surfactant. , Flame retardant, filler, etc. may be blended in an appropriate amount.

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples. Unless otherwise specified, parts are parts by mass.

(Examples 1 to 10, Comparative Examples 1 to 4)
20 parts of polyester polyol (number of hydroxyl groups: 2, number average molecular weight 5,000) containing adipic acid and 1,6 hexanediol as main components, which have been dehydrated in advance by a vacuum dryer, and adipic acid and ethylene glycol as main components. 25 parts of polyester polyol (number of hydroxyl groups: 2, number average molecular weight 2,000), 25 parts of polyester polyol (number of hydroxyl groups: 2, number average molecular weight 2,000) containing isocyanate and neopentyl glycol as main components, and azeline 5 parts of polyester polyol (number of hydroxyl groups: 2, number average molecular weight 8,000) containing acid and ethylene glycol as main components, and polypropylene glycol (number of hydroxyl groups: 2, number average molecular weight 2,000, manufactured by Asahi Glass Co., Ltd .: EXENOL2020) Mix 25 parts, 20 parts of diphenylmethane diisocyanate (number of isocyanate groups: 2, manufactured by Nippon Polyester Industry Co., Ltd .: Millionate MT) and 0.5 part of polybutene (manufactured by Nikko Co., Ltd .: HV-30SH), and add a predetermined amount uniformly. After mixing, the reaction is carried out at 110 ° C. for 2 hours, further defoamed and stirred at 110 ° C. for 2 hours under reduced pressure, and the reactive hot melt adhesive containing the urethane prepolymer (i) having an isocyanate group and the non-reactive component (ii) is contained. The composition was obtained. Table 1 shows the composition of each adjusted adhesive.

The test results and evaluation methods of the produced reactive hot melt adhesive composition (Examples 1 to 10 and Comparative Examples 1 to 4) will be described below.

<Viscosity (melt viscosity)>
The measurement was performed under the following conditions using a BH-HH type small amount rotational viscometer (manufactured by Toki Sangyo Co., Ltd.).
Rotor: No. 4 rotor Sample amount: 15 g
Rotation speed: 50 rpm
Temperature: 120 ° C

<Mechanical characteristics>
The prepared reactive hot-melt adhesive composition sample was melted at 100 ° C. to prepare a film of an adhesive layer of length 15 mm × width 40 mm × thickness 100 μm, and left in a constant temperature bath at 25 ° C. and 50% RH for 7 days. The mechanical properties (tensile elastic modulus (MPa), tensile fracture stress (MPa), breaking point elongation (%)) of the adhesive layer are set according to JIS K-7127, which is a tensile tester (Auto manufactured by Shimadzu Corporation). It was measured using the graph AGS-X).

<Adhesive strength>
The prepared reactive hot-melt adhesive composition sample was melted at 100 ° C. and placed on a polycarbonate plate at a temperature of 25 ° C. and 50% RH (relative humidity) on a polycarbonate plate (length 15 mm × width 40 mm × thickness 100 μm). After forming a film of the adhesive layer of, it is pressure-bonded to a polycarbonate film of length 250 mm × width 25 mm × thickness 100 μm, and left in a constant temperature bath at 25 ° C. and 50% RH (relative humidity) for 7 days to perform a 90 ° peel test. (Peel speed: 100 mm / min) was performed, and the adhesive strength was measured.

<Impact resistance>
The prepared reactive hot melt adhesive composition sample was melted at 100 ° C., and a silica container (PSY-manufactured by Musashi Engineering Co., Ltd.) equipped with a precision nozzle (SHN-0.25N manufactured by Musashi Engineering Co., Ltd.) having an inner diameter of 0.25 mm was attached. 30E) and discharged using a dispenser (SHOTMASTER 200DS manufactured by Musashi Engineering Co., Ltd.) preheated to 100 ° C., and adherend A (polycarbonate plate: width 100 mm x length 50 mm, inner diameter 20 mm at the center). A 40 mm x 40 mm square is applied on the hole), and the adherend B (acrylic plate: width 50 mm x length 50 mm) is adhered to the adhesive to have a width of 0.5 mm and a thickness of 0. The laminate was adjusted to 1 mm to prepare a laminate. The laminate was left to stand for 3 days in an environment of 23 ° C. and 50% RH (relative humidity), and the laminate was prepared in an environment of 23 ° C. and 50% RH (relative humidity). Then, the adherend A side of the laminated body was fixed to the Dupont impact machine with the adherend B side facing downward. Next, a shooting type (radius 6.25 mm) was formed in the hole of the adherend A of the laminated body. It was arranged so as to be in contact with the surface of the adherend B on the side to which the adhesive was applied from above.
After that, a weight having a load of 300 g is dropped from heights of 200 mm, 250 mm, and 300 mm above and collides with the shooting mold to apply a force downward in the vertical direction to the adherend B of the laminate to apply the adherend. It was confirmed whether or not B was peeled off. As a result, those that did not peel off were evaluated as "○", and those that did peel off were evaluated as "x".

It can be seen that each sample of Examples 1 to 10 which is the reactive hot melt adhesive composition of the present invention has excellent impact resistance.
On the other hand, Comparative Examples 1 and 2 did not contain the non-reactive component (ii) and the polyester polyol (A-2-2), so that the elongation was low and the impact resistance was poor.
Further, in Comparative Example 3, since the polyester polyol (A-1) was not contained, the tensile fracture stress was low and the impact resistance was poor.
In Comparative Example 4, since the polyether polyol (B) was not contained, the tensile elastic modulus was high, but the elongation was low and the impact resistance was poor.
Comparative Example 5 was an embodiment containing 20 parts of the non-reactive component (ii), but had poor adhesiveness and impact resistance.

Claims (1)

A urethane prepolymer (i) having an isocyanate group obtained by reacting a polyester polyol (A), a polyether polyol (B) and an isocyanate (C), and a component (ii) that does not react with the urethane prepolymer (i). Reactive hot melt adhesive composition contained
The polyester polyol (A) is composed of a crystalline polyester polyol (A-1) and an amorphous polyester polyol (A-2).
The amorphous polyester polyol (A-2) is composed of a polyester polyol (A-2-1) having a molecular weight of 3,000 or less and a polyester polyol (A-2-2) having a molecular weight of 5,000 or more.
The urethane prepolymer (i) and the non-reactive component (ii) are selected from polybutene, polybutadiene, ester plasticizer, rosin resin, rosin ester resin, hydrogenated rosin ester resin, terpene resin and hydrogenated terpene resin. Or more than one
The amount of the component (ii) that does not react with the urethane prepolymer (i) is 0.1 to 10 parts by mass with respect to 100 parts by mass of the urethane prepolymer (i).
The mechanical properties of the obtained adhesive layer are a reaction in which the tensile elastic modulus specified by JIS K-7127 is 40 MPa or less, the tensile fracture stress is 15 MPa or more, and the elongation at break is 1,000% or more. Sexual hot melt adhesive composition.